1. Field of the Invention
The present invention relates to an apparatus for the production of mineral fibers and felts formed from the mineral fibers, and more particularly refers to such an apparatus which can produce mineral fiber felts of uniform thickness and density.
2. Description of the Prior Art
It has been conventional in the prior art to produce glass and mineral wool fibers by conveying a stream of molten material such as glass or slag onto a rotating surface. The molten material is thereby centrifuged into the path of a high velocity stream formed of super-heated steam, the centrifuged material originally in the form of finely divided molten streams is blasted by the steam and formed into solidified material of fibrous form. Among the patents which disclose this method are U.S. Pat. Nos. 2,869,175, 2,944,284, 3,013,299 and 3,022,538. However, the processes disclosed using steam were not completely satisfactory, since, the relatively high velocity and impact force of steam caused an undesirable attenuation and severance or breakage of the mineral fibers, thereby reducing the efficiency of the apparatus and the quality of the finished product. Moreover, the use of steam required rotor speeds of the centrifugal apparatus to be kept within critical limits in order to obtain filaments of a desired diameter. For example, where speed of the rotating disc was too high, the secondary attenuation produced thereby resulted in loose fibers which were too thin and fragible for normal use. Further, the fibers produced were of extremely short length and did not assume the structure of elongated threads or fibers. In order to overcome the deficiencies of steam operated fiberizing equipment, a method and apparatus were disclosed in U.S. Pat. No. 2,882,552 for using compressed air of low pressure to avoid the undesirable effects resulting from the use of high pressure steam. In the use of compressed air an advantage was realized in that no secondary attenuating defects were realized and the tendency to break or sever the filaments into short lengths was eliminated. However, the method and apparatus disclosed in that patent were not as efficient as desired and the quality of the mineral wool produced still left something to be desired with respect to the quality and the surface uniformity and smoothness of the finished fibers. Moreover, the apparatus disclosed in the patent is awkward to load and difficult to operate. The apparatus takes a lot of attention, is erratic, produces low yield and a high ratio of shot to fibers.
In U.S. Pat. No. 4,106,921 there is disclosed an apparatus for the production of mineral fibers utilizing compressed air and which apparatus can provide excellent mineral fibers of improved quality and at a reduced cost.
It has been conventional in the formation of felts, batts, or blankets of mineral fibers to deposit the formed fibers on a conveyor belt to form a layer of fibers. The layer is then moved to a rolling station where the fibers are compressed into the batts, blankets or felts. However, although the roll assembly insures that a felt or blanket of uniform thickness will be produced, because the fibers are not always piled on the belt to the same height or thickness, where the thickness of uncompressed fibers is greatest, the resulting density will be greater than that of the areas where the fibers are not piled as high.